Carburetor for internal combustion engines



H. v. SELD 2,7 6,

CARBURETOR FOR INTERNAL COMBUSTION ENGINES Dec. 6, 1955 6 Sheets-Sheet 1Filed Jan. 14, 1953 Mum/pr HANS l SELD WW5,

. 6, 1955 H. v. SELD CARBURETOR FOR INTERNAL COMBUSTION ENGINES FiledJan. 14, 1953 6 Sheets-Sheet 2 INVENTOR. HANS V- $51.0 BY

M 4 Zn/ AGT 6. 1955 H. v. SELD 2,726,073

CARBURETOR FOR INTERNAL COMBUSTION ENGINES Filed Jan. 14, 1953 6Sheets-Sheet 5 Awe/Mar HANS V. S E LD 6, 1955 H. v. SELD CARBURETOR FORINTERNAL COMBUSTION ENGINES 6 Sheets-Sheet 4 Filed Jan. 14, 1953 EM 3 m5M T mv M S w E Q. Q [@E Dec. 6, 1955 H. v. SELD CARBURETOR FOR INTERNALCOMBUSTION ENGINES 6 Sheets-Sheet 5 Filed Jan. 14, 1953 INVENTOR. HA N6V. SELD AGT Dec. 6, 1955 H. v. SELD CARBURETOR FOR INTERNAL COMBUSTIONENGINES 6 Sheets-Sheet 6 Filed Jan. 14, 1953 R. 0 D y W T L m x M N G lM A 5 m mm Y B .0 m 0% MED United States PatentO CARBURETOR roR INTERNALGOMBUS QNv 1 ENGINES Hans V. Seld, Planeg g, near Munich, Germany,assigner to Firm Metallbau Semler G'cm. H.-, Munich, Munich, Germany Thepresent invention relates to carburetors for internal combustiqn n nes,nd is Pa t u a ly d recte t6 a carburetor for an internal combustionengine having a radially variable throat section, and wherein thecrosssection of the throat section is varied without deviating from theh re hi ar s ow by e odrnam s e 'y to be the most favorable for the flowof fluids in tubes and is clear of any obstructions which mightinterfere with smooth or laminar flow through the throat section.

The interior surfaces or passages of conventional carburetors areusually formed with abrupt changes in crosssection and have interferingelements, such as, for example, the throttle or butterfly valve, thechoke valve, the fixed venturi and the discharge nozzle, located in theflow path of fluids through the throat section, so that the flow offluids through the carburetor is not streamlined or laminar. In these.conventional carburetors, the diameter o t e en u i ec on s usua l sub ti ly smaller than the diameter of the inlet to the engine manifoldthereby limiting the fuelisupply to the 'engineat high p ed d. a s qwng' u s ee s tbs d ame e of the venturi section is too large and resultsin a relatively slow passage of the air through the venturi which causesnon-uniform mining so that the fuel-air mixtur e delivered to the enginemanifold contains overly large fuel particles. Since the fuel dischargenozzle is locatedahead of the throttle or butterfly valve inconventional carburetors, the pressure at the fueldisicharge nozzlevaries only slightly with the various operating'conditions and it istherefore difficult to make 'the actual supply of fuel conform to thereal fuel requirements forthe various operating conditions. r i

In the past, attempts have been made to obtain satisfactory fuelairmixturesover the entire range of operating conditions by providingcarburetors having complex air intake arrangements employed inconnection with multiple fuel discharge nozzles, but the resulting fuelconsumption was still far less favorable than that obtained in enginesequipped with fuel injectionsystems. So long as a fixed venturi isernployedfit is impossible to avoid the unsatisfactory compromiseinherent in that element, namely inadequate mixing atslow engine speedsand reduced engine output at high speeds.

Accordingly, it is -an object 0f the present invention to provide acarburetor for internal combustion engines which inculdesaventuri'having a cross-sectional area variable between zero and thecross-sectionalarea of the inlet to the engine manifold and arranged sothat the shape of the venturi, at all conditions of operation, conformsto that which aerodynamic theory indicates is most favorable forstreamlined flow for the respective conditions of operation. 1

Another object is to provide a carburetor constructed so that aradialetfect is obtained to causeefiicientmixing of the fuel and air ata low pressure zone in the center of, the flow even during operatingconditions resulting in. a very. slow air ow rthrough the carburetor.

M her s 's s to as id a. ai -pis e 9 th s 2. scribed character whereinthe cross-sectional area of the venturi is controlled automatically in"response to variations in the vacuum inth'e' engine intake manifold, andthis automatic cdnlt'rolissuperimposed upon the'control of the venturicross-sectional area as exercised by'the operator.

Another object is to provide a carburetor of'the described characterwhich has asingle, 'co'ritinuouslyyariable fuel discharge nozzleconstructed so that'it cannot become cloggedQand wherein the atomizationof th'e'fuel occurs in three stages to produce aparticu1ar1yiinefuelfair mixture. ...i

Still another object is to provide a carburetor of the describedcharacter which permits a high degree of overloading of the associatedengine so that engine may be driven in high gear evenat relativelylowspeeds.

A further object is to provide a carburetor of the described characterwhich, when associated with an internal combustion engine, improvestheaccelerat'ion', hill climbing and high speed performance of theengine, and which is substantially unatfectedby temperature changes sothat the associated engine may be operated at'its'top speed immediatelyafter acute start.

In accordance with the present invention, the intake portion" of thecarburetor throatis shaped accordirigto an ideal fiow hyperboloid, withthe diameter thereof, gradually diminishing to that of the'intake'rrianifold of the associated engine and the reduction ofdiameter'cor responding to the theoretically determined magnitude" ofair friction. Further, for -o'pera' tion at partial throttle, the abovedescribed basic form is modified so that "ideal flow hyperboloids areprovided'which reduce to; afdiar'neter smaller than that of theengineintake manifold and each of which" is followed by theoretical venturi'and then a corresponding Laval valve Widening to the diameter of theintake manifold. Even at idling speed, the passage through the'carburetor'presents ideal'flow hyperbolas which taper to zero and leadto an adjoining venturi and a Laval valve. Because 'ofthe hyperbolicconfiguration of the throat passagefopening of'the passage from'theidling condition results in the air immediately following the prescribedpathof intake s o that' the acceleration of the air stream through thecarburetor approaches the theoretically maximum value possible, and thecontinuous transformation of energy between its potential and kineticforms is avoided. Further, carburetors embodying the above featuresachieve substantial difier ences in thevacuum at the fuel dischargenozzle in response to' different operating conditions,and thesedifferences in vacuum are comparable to those obtain'ed ina conventionalcarlit re'torin which the throttle valve is omitted a'nd'ope'ttion iscontrolledonly with a choke valve located ahead of the fuel dischargenozzle. f In order that the present invention maybe easily understood,illustrative embodiments are shown the accornpanying drawings forming apart hereof and whereinf Fig. lais a schematic view showing'the idealax-ial ss vs ma e m an ma -11 stma a er mbo yi he esen .luvcntiun'i heno th qt g. 9 d m i. u Fig. 1b is a schematic view similar toF ig. labutfor partial throttling;

passage therethrough shaped in accordance with the principlesillustrated in Figs. 1a, 1b, lo and 1d;

Fig. 3 is a view similar to Fig. 2, and showing the carburetor in theidling and no throttling conditions;

Fig. 4 is an axial sectional view of a down-draft carburetor embodyingthe present invention and adapted for association with the internalcombustion engine of an automobile, with the view being taken along theline AB-C of Fig. 5;

Fig. 5 is a bottom plan view of the carburetor of Fig. 4;

Fig. 6 is an axial sectional view of another embodiment of the presentinvention; 7

Fig. 7 is a view similar to Fig. 6, but with internal parts of thecarburetor being shown in elevation;

Fig. 8 is an elevational view of an assembly disposed within thecarburetor of Fig. 6;

Fig. 9 is a sectional view taken along the line 9-9 of Fig. 6; v

Fig. 10 is a sectional view taken along the line 10-10 of Fig. 6;

Fig. 11 is an axial sectional view of a carburetor for a racingmotorcycle constructed in accordance with another embodiment of thepresent invention; and

Fig. 12 is an axial sectional view of a carburetor for motorcyclesconstructed in accordance with still another embodiment of the presentinvention.

Referring to the drawings in detail, and initially to Figs. la, 1b and1c thereof, it will be seen that the ideal axial cross-section throughthe intake flow in a carburetor is defined by hyperboles a tapering orconverging to a diameter 1 which is the diameter of the intake manifoldof the associated internal combustion engine (Fig. la). At slow enginespeed or partial throttling (Fig. 1b), the hyperboles a are followed byan ideal venturi b which widens in the direction toward the intakemanifold in the shape of an ideal Laval valve, as at c, to the diameter7 of the intake manifold. Similarly, during idling, the ideal axial flowcross-section (Fig. 1c) includes hyperboles a coming together at theventuri b and then widening to the intake manifold diameter f at a Lavalvalve section c. In this description, the phrase Laval valve section isused to denote a passage of conically increasing diameter wherein theangle between any portion of the wall defining the passage and the axisof the latter is no greater than 8 degrees.

In Fig. 1d the air flow is assumed to be in the direction of the arrow Aand the vertical distances between the flat horizontal plane and thevarious curves thereabove represent the annular dimensions of thecarburetor flow passage for different operating conditions. Thus, thevertical distances between the horizontal plane and the uppermost curve,representing the outer wall of the flow passage, indicate the idealradial dimensions for the no throttling condition, and the verticaldistances between the horizontal plane and the two other curvesincluding the hyperboles a, venturis b and enlarging sectionsc, indicatethe ideal radial dimensions of the flow passage for partial throttlingand for idling, respectively, The shaded area between the uppermost andlowermost curves in Fig. 1d represents the variation in the totalopening through the carburetor depending upon the relative positions ofthe parts of the carburetor defining the flow passage through thelatter. The ideal intake configurations represented by Figs. la, lb, 10and 1d need not necessarily be radially symmetrical.

In Fig. 2, the passage through a carburetor embodying the presentinvention is shown schematically in axial section with the passage beingformed in accordance with the principles illustrated in Figs. la, lb, 1cand 1d. Thus, the ideal flow hyperbola a has had the shaded area of Fig.1d taken therefrom and the widened outer wall is represented at d, andthe volume between the-ideal hyperbola a and the enlarged surface d issuperimposed on the surface of an inverted cone to provide a concaveconical surface 2 on the member 3 which is supported for axial movement.Since the area between the curves a and d, representing the enlargementof the intake passage, has been added to the member 3 to similarlyreduce the cross-sectional area of the intake passage, it is apparentthat the latter will vary in accordance with the curves of Figs. 1a, 1band 1c depending upon the axial position of the member 3 relative to thewall d. Thus, in Fig. 3, the full line position of member 3 representsthe idling condition of the carburetor and the broken line position ofmember 3 represents the completely unthrottled condition. From Fig. 3 itcan be seen that the space between the generally conical member 3 andthe wall d of the carburetor throat consists of a fixed portion and avariable portion which is defined by the difference between the brokenand full-line positions of the member 3. The fixed and variable portionsof the space together yield the ideal flow section of Fig. ld and thecourse of this ideal flow section may be changed linearly by axialmovement of member 3 and quadratically by radial movement.

The transformation of the section shown in Fig. 1a into an annularsection, as in Fig. 2, provides a radial flow effect at the vertex ofthe member 3 since the air flow tends to follow the concave curvature ofwall surface e which defines the air path and the air flow velocityincreases because of the decrease of surface area at the vertex ofmember 3. Thus, even when the carburetor is in its unthrottledcondition, a zone of reduced pressure is created at the vertex of member3 to extract a fuel froth mixture from an opening (later described indetail) at the vertex, and this mixture is fully atomized into a fog inthe throat g (Fig. 2).

In Fig. 4 an actual embodiment of the present invention is illustratedin detail and represents a down-draft carburetor for use in associationwith an automotive internal combustion engine. The carburetor of Fig. 4includes a lower body 38 having an upstanding cylindrical passage formedtherethrough and a flange 45 at its lower end for mounting upon theintake manifold (not shown) of an associated internal combustion engine.The flow passage 2 through the carburetoris defined by the outer surfaceof a throttle body 3 having the shape of the surface e in Figs. 2 and 3,and the internal surface of a flaring intake pipe 1 having the shape ofthe surface d in Figs. 2 and 3. At its lower portion, the intake pipe 1is formed with a cylindrical outer surface received in the upstandingcylindrical passage of the lower body 38 so that the intake pipe 1 ismovable axially, up and down, relative to the lower carburetor body 38.A rim 39 is formed at the upper edge or periphery of the flaring intakepipe 1, and a flexible seal or diaphragm m extends between the rim 39,to which it is clamped, and the adjacent wall of the carburetor body 38.The carburetor body 38 is shaped internally to provide a space 40opening upwardly against the underside of the flaring top portion ofintake pipe 1, and the membrane m acts to seal the space 40 fromcommunication with the flow passage 2 defined between the internal andexternal surfaces of the intake pipe 1 and the throttle body 3,respectively. A spring abutment is secured on the exterior of the intakepipe 1 within the space 40, and compression springs 42 (one being shownin Fig. 4) are interposed between the abutment on intake pipe 1 andadjustable abutments or supports 44 at the bottom of space 40 so thatthe springs 42 yieldably urge the intake pipe 1 upwardly or in the axialdirection causing restriction of the flow passage 2.

In order to efiect control movement of the intake pipe 1 in response tovariations in the vacuum created in the intake manifold of an associatedengine, the lower body 38 of the carburetor is formed with internalducts or passages 41 which extend from the space 40 and open radiallyinward into the carburetor throat g at locations adjacent the mountingflange 45. A valve V having a flow regulaing orifice 43 is interposed ineach duct 41 and provides limited communication between the space '40and the lower part of the throat g. Since the pressure ayzango'zs in thethroat g, and hence in the space 40', will be inorc or less'lowen thanthe pressure in the passage 2, a force will act" downwardly: on theintake pipe 1 against the force exerted: by the springs 42'; Thus, theposition of the intake: pipe I for any: operating condition will bedetermined by therelationship of the spring forces and the pressureunbal'anceibetween. passage 2 and space 40.

The carburetor of Fig. '4 further includes an upper body'46 which isclamped to the upper edge of the lower body 38, with the. outer edge ofthe membrane m being secured-betweentheclamped together edges of thelower and upper bodies; Stops 53 are provided on the interior of upperbody 'to limit the upward. movement of the intake pipe. 1, andthesestops may be adjustable, if desired; The upper body 46 is. formed withan air inlet atone sidef'to which". a. suitable air filter 6 is securedtangentially sothat 'the primary enters the passage 2 from the filter 6.The upper body 46 is formed with a cup shaped? depression at the tophaving a hollow, open ended cylindrical wall 16 extending upwardly fromthe centerthereof. The depression 5 defines a float chamber around theupstanding cylindrical'wall 16.

The outer wall of the depression 5 is cylindrical and the throttle body-3 is formed with a recess corresponding in shape to the recess 5 so thatthe throttle body 3 fits over the depression 5 and is movable axiallyand rotationally relative: to the latter. In order to effect axial movement ofthe throttle body 3 for regulating the flow passnge z,asltirthdepen'ds from the top of upper body 46 concentric with recess 5and is formed with external threads 19 of large pitch, and the throttlebody 3, at its upper portion, is formed with a cylindrical outer rimextendin'garound-the slcirth and having a helical groovellEl'ilIS-tll'llfil'l'lfil surface .engaging the threads 19, so that thethrottle "body 3 is axially displaced relative to the carburetorbodywhen-the throttle body is rotated. Rotation ofithe throttle body :3 iseffected by a Bowden cable :20 connected thereto and extending out ofthe upper body '46for manipulation :by suitable operator controlled-:-means (not shown). Whiletheembodiment of the invenvitioniillustrated:in Fig. 4 eflfects vertical movement of zthrottle body :3 by .a threadarrangement and means for rotating thethrottle body, :itjs apparent thatother conventional mechanisms maybe employed for effecting such verticalmovement.

A: cover is provided for thefloat chamber 5 and includes a lower portion9 and an upper portion 47 which are *superposed'with'a fuel filter 27interposed therebetween. A .fuelwsupply p'ipe29 CQILHBtGSitO an inletcoupling-on the upper portion 47 and the fuel passes downwardly from"the-coupling :through .a passage 12 and into a dirt and water trap 28:formed in the lower portion 9 of the cover. fFrom the-trap 28,"thefuelpasses upwardly through the filter 27 .intora channel defined by ashallow groove in the-bottom surface-"of cover portion 47 and whichconducts the fuel to a location over a:c.onventional needle valveassembly '18. A ring-:'shaped-float 17 is provided in the float-chamber5 ;and:is.free"to rise, fall and tilt with the levelofr'the'fuel withinthe'float chamber. The float 17 and valve assembly 18 cooperate tomaintain the level of fuel in chamber 5 substantially at the level 52inthe usual manner. .That'is, the valve assembly 18 .is'normally opentopermitiflow 'of fuel into chamber '5 and, when the-level of the fuelrises above the line 52, the .float17- engages-[the valve :assembly .18to close-the rlatter-until the fuel level hascreceded.

An axialzbore 35 iszformed in'the cylindrical wall 16 and opens at the'bOttOIIYiHtOZthG float chamber 5 to receive fuel from :the :latter and:deliver such fuel to a preliminary mixingarrangement which will now bedescribed.

A central axial bore .32'textendsthrough the throttle body -3:and opens:at its lower:end:rat the vertex .or tip 30 of the onion-shapeduoutersurface ;of:the body13. An atomizing :or dispersing plate .-P is 1disposed at "the ;lower open end 0f the bore'32,"andithewbore1327isuunder theiinfiuence of the:low pressureproducedat the throats cfthe a ure tor. A cylindrical extension- 3: pr jects;upwardly fr m the center of the throttle body 3, and is'received withinthev cylindrical wall 16 of theuppcr body 46 to. assist in guiding thevertical movements of he throttle body and to house the preliminarymixing arrangernent. The bore 32 passes, through the extension. 33 and;at: its upper end opens into, a counter-bore. of enlarged diameter inwhich a cylindrical air intake nozzle 7 ismounted. A, needle valve 8 isalso carried by the extension. 33 of the throttle body 3 concentric withthe nozzle 7 and within the latter. A fuel nozzle 1: includes a radialflange seating on the upper edge of cylindrical wall 16 and adependingcylindrical portion. extending around the valve 8 in the space k definedby the air intake nozzle 7. A cover plate 48 is superposed on the radialflange of the nozzle x and the bore 35 opens at its upper endthroughahole in thisz radial flange so that the fuel from chamber 5passes-throughbore 35 above the flange of nozzle xvand into a C i y 9dc.- fined' between the topv of nozzle x and'the cover plate 48. Thefuel from cavity 49 flows downwardlythrough the annular space it definedbetween the needle 8 and the low.- .er edge of the nozzle x and over a.downwardly flaring conical portion y of the needle which has a sharpedge at its, base. It is apparent that vertical movement of the throttlebody 3 produces axial displacement of the needle 8 relative to thenozzle x and thereby varies thearca of the annular space it to regulatethe flow of fuel,

The air for preliminary mixing is supplied through a filter 10 securedon the top of wall 16 above the cover plate .48 and through a passage'13 formed in the cover plate and the radial flange of nozzle x. The airfrom pas sage 13 enters into a radial space between the top of airintake nozzle 7 and the lower surface of the radial flange at the top ofnozzle x. At the top ofair intake nozzle 7,, an inwardly directedannular lip .67 .is formed, and the outer surface of the cylindricalportion of nozzle xis bulbous, as at 34, so that the area of the annularspace defined between lip 67 and the outer surface 34 variesas thethrottle body 3 and the nozzle 7 are displaced vertically relative ,tothe body 46 and the nozzle x to.control.the admission of air into thespace k between the nozzlesx and 7. The air passes through annular spacek andmixeswith the fuel which flows over the cone y andtears-away fromthe sharp edged base of the latter. ,Athrottling ring ,zsurrounds thelower or base edge of thecone y, and the inside edge of ring 2 and thebase of cone y define an annular slot w therebetween. The preliminaryair-fuel mixture flows'radially inward fromthe space w into an axialbore 68 formed in the lower portion of needle 8 :and opening downwardlyinto the bore 32. ,Itis apparent that the. vacuum at g will becommunicated through ,:the b,ores 32and =68 to the space k-and that ,thedifferences in pressure between locations in spacek and the;pressure atg will vary as the throttle body is axially displaced to changethe areaof the annular space between lip 67 and nozzle x.

The lower portion of needle 8 having theaxialtboreos therein, is spacedfrom the wall of bore 32 so that an annular channel or vent 51 is formedtherebetween. The vent ,51 opens into a chamber 4 around the lowerportion of the-needle valve '8, and passages 0 are providedin theextension33 and the cylindrical wall 16 for bringing air from theopening 13 to the 'chamberc4. Thus, airfrom chamber 4 passes throughannular vent .51 to provide ;a further mixing of air with thepreliminary air-fuel mix- .ture as the latter emerges fromv-bore68 intobore.32. 'It should also be noted that the air delivered through theannular vent 51 provides-a layer of air adjacent'the wall of bore 32 sothat the air-fuel mixture emerging :from bore '68 flows through the bore32 almost without coming in contact with the walls of the latter.

.The parts described above in the .arrangementfor preliminary air-fuelmixing are dimensionedso that the an- :nular slot for admitting :airdefined betweensurface 34'of :nozzle :xfian'd .lip 67 :decreases in areaiwhen the throttle body 3 is displaced in the direction increasing thearea of the annular slot u for regulating the fuel flow. Thisrelationship, in conjunction with the action of throttle ring 2,compensates for substantial variations in the low pressure at thedischarge opening 50 at the lower end of bore 32. Further, the needle 8has a contour, in the portion thereof cooperating with the lower edge ofnozzle x to define the slot a, which is curved or shaped to conform tothe fuel demand curve of the associated engine. The annular space kwhich is limited at the top by the lip 67 and varies in volume as thethrottle body 3 is vertically displaced acts as an accelerator. That is,when the body 3 is suddenly moved upwardly, the volume of space k isincreased to further lower the pressure therein so that the flow of aspurt of fuel is induced through the annular slot u to satisfy thesudden increased demand for fuel.

In order to permit movement of the throttle body 3 relative to the upperbody 46, the space 36 between the bottom of the float chamber and theinterior of the throttle body is vented by a passage 37 which opensdownwardly into the flow passage 2. Further, when the throttle body 3 ismoved upwardly from the idling position, air

' flows out of chamber 36 through the passage 37 to avoid sticking ofthe intake pipe 1 to the body 3.

To provide for the delivery of an air-fuel mixture during idling, radialgrooves 11 are formed in the surface of the throttle body 3 andcommunicate with passages L which open into the chamber 4 above theannular vent 51. When the body 3 is lowered to its idling position, thezone of lowest pressure shifts from a location at the tip 30 of the body3 to locations in the passage 2 adjacent the grooves 11, so that thepreliminary air fuel mixture then emerging from bore 68 travels upwardlythrough vent 51 into chamber 4 and thence through passages L fordischarge at the grooves 11 into the air stream in flow passage 2. Whenthe throttle body 3 is again raised, the area of low pressure shifts tothe point 30 and the flow through passages L is then in the directionfrom the grooves 11 to the chamber 4. This additional air supply to thechamber 4 compensates for the reduced air intake through the annularslot between the lip 67 and surface 34 of nozzle x, since as previouslymentioned the area of this slot decreases as the throttle body is raisedand the area of slot u is increased.

The concave portion of the outer surface of throttle body 3 may bevaried. For example, decreasing the radius of curvature of the concaveportion produces a stronger radial flow effect and results in moreeconomical utilization of the fuel, while increasing the radius ofcurvature reduces the change in direction in the incoming air stream inflow passage 2 and provides greater supply of fuel to the engine.

Referring now to Figs. 6 to 10, inclusive, a simplified carburetorprimarily intended for a motorcycle and embodying the present inventionis there illustrated. While the carburetor is shown in Figs. 6, 7 and 8with the axis of the movable throttle body extending vertically, it isto -be understood that the carburetor, when mounted on a motorcycle, isarranged so that the axis of the throttle body thereof is eitherhorizontal or only slightly inclined relative to the horizontal with theright hand portion of the carburetor, as viewed in Fig. 6, beinglowermost.

In'the embodiment of Figs. 6 to 10, the flaring intake pipe 1, having aninternal surface similar in shape to the surface d of Figs. 2 and 3,also forms the body or casing of the carburetor and is fixed to intakemanifold (not shown) of an associated internal combustion engine by asplit collar In at its converging end which is secured by a clampingbolt 1b (Figs. 6 and 7). Further, the side of the flaring intake pipe 1to the left of Fig. 6 and which is uppermost in the installed positionis formed to provide a rain shield. A cylindrical air filter 6 isdisposed between the flaring intake pipe 1 and a cover 9, with axialbolts 31 (Figs. 9 and 10) being provided to .secure together the cover.9and pipe 1 with the filter 6 clamped therebetween. The cover 9 is formedwith a hollow structure depending therefrom to form a fuel filterchamber, and the fuel filter chamber defining structure has an arcuateouter wall portion and a chordal inner wall portion. A float valvechamber 5 is open at one side and at the top and is sealed at the openside and top by the cover 9. The outer walls of the structure dependingfrom cover 9 to define a fuel filter chamber and of the float chamber 5together form a cylindrical surface having a continuous helical thread19 thereon (Fig. 8).

A throttle body 3 having an outer surface similar to the surface e ofFigs. 2 and 3 is provided with a cylindrical recess opening toward thewide end of the body to receive the float chamber 5 and the fuel filterchamber of the cover 9. The cylindrical recess of body 3 is formed witha helical groove therein receiving the thread 19 so that rotation of thethrottle body 3 will cause axial displacement thereof towardand awayfrom the flaring intake pipe 1. Rotation of thethrottle body 3 iseffected in one direction by a Bowden cable 21 (Figs. 9 and 10) whichenters the cover 9 tangentially to the thread bearing surfaces of thebody 3 and the cover 9 and float chamber 5, and at the pitch angle ofthe threads. The cable 21 is received in a suitable groove 20 (Fig. 9)in the external surface of the float chamber 5 and connects to anattachment on the body 3 so that tension on the cable 21 causes the body3 to rotate in one direction. A spring 22 is also connected to the cableattachment on the body 3 and to the float chamber 5 (Fig. 9) and acts torotate the body 3 in the opposite direction when the tension in cable 21is relaxed.

Fuel is admitted to the carburetor of Figs. 6 to 10 through a fuel line29 which is coupled to a filter cap 28 threaded in the cover 9. A filteror cup-shaped screen 27 depends from the cap 28 and is received in thefuel filter chamber depending from the cover 9. Thus, fuel flowsoutwardly through the foraminated wall of the filter 27 into thesurrounding fuel filter chamber. As seen in Fig. 9, a fuel passage leadsfrom the fuel filter chamber to the float chamber 5 which contains asubstantially semi-circular float 17, and a float operated valve 18 isinterposed in the fuel passage leading from the fuel filter chamber tothe float chamber. When the fuel level in the float chamber has reacheda predetermined level, the float 17 engages valve 18 to close the latterthereby maintaining the fuel at the predetermined level.

' The body 3 is formed with a discharge nozzle 30 at the vertex of theouter surface thereof, and the nozzle 30 communicates with adiametrically enlarged chamber 4 within the throttle body 3. A tubularextension 32 is fixed axially to the tubular body 3 and extends slidablyand rotatably through a cylindrical member 16 which axially traversesthe float chamber 5 and is fixed to the latter. A needle valve 8 and airintake nozzle 7 extend concentrically from the end of tubular extension32, and a fuel nozzle x is carried by the end of cylindrical wall 16,the valve 8, and nozzles 7 and x cooperating in the manner described inconnection with the embodiment of Figs. 4 and 5 to meter and effectinitial mixing of the air and fuel mixture.

The air for initial or preliminary mixing of the air and fuel entersthrough a passage 13 (Fig. 10) and grooves 14 in the cylindrical member16 forming the nozzle housing, and the admission of this air is variedin the manner previously described. Fuel for the preliminary mixingenters the arrangement described above through a bore 35 in the cover 9extending from the fuel chamber 5. Additional air is mixed with thepreliminary air-fuel mixture emerging from the tubular member 32 intothe chamber 4 ahead of the discharge nozzle 30 through channels L whichcommunicate with the high pressure zone of fiow passage 2 through radialbores 11. Thus, under normal operating conditions, the pressure at 11 ishigher than at the vertex nozzle 30 of the body 3, and

carburetor isv prevented.

amn on air flows throughibores 11 andpassa'geszL into thechamher 4. Whenidling conditions prevail, thepressurerattthe bores .11 isless than thepressure at the discharge nozzle -30 and the air-fuel mixture flows fromtherchamber ":4 :into the passages L and is discharged fromthezboresll,--which then serves as atomizing nozzles.

.In order to limit the rotational movement rof ':the throttle body 3 inthe direction causing idling, a"stop 124,

:Fig. 7, is provided on the throttle body and is engaged by anadjustable abutment screw 23' extending tangentially .t-hrough theintake pipe or body. 1.

'Arich mixture or additional fuel for starting is'ob- When the .plunger26 is obtained for starting.

The carburetor illustrated in Fig. 11 is primarily in- \tended-for useas a motorcycle racing carburetor and;

as in the embodiment of Figs. 6 to 10, the flaring:intake pipe 1 isstationary and forms part of thecarburetor "body or housing rather thanbeing movable in response to variations of vacuum in the intake manifoldof the engine,.as in'the embodiment of Figs. 4.and 5. The" flaringintake pipe 1 has an internal surface-.similar'to the-surface d-of Figs.2 and 3, and a throttle body -3,

movable axially relative to the pipe 1, is formed 'withua concavesubstantially conical outer surface similar to the -vertex portion ofthe surface e of Figs. 2 and. 3. The" gperiphery of .throttle body 3 inFig. 11 is extended to .form an air scoop 80 curved in the directiontoward the flared pipe 1 and operating to catch theair rushing: past thecarburetor and reverse the direction 'ofrmovement a of suchair forradial feeding into theflow passage 2 of .the carburetor therebymaterially enhancing the suction eifectof such radial flow.

iThe carburetor of Fig. 11 includes a fuel bowl. 5-which .has a.cylindrical outer surface and extends'slidablyainto va correspondinglyshaped recess in thethrottle body .3. Further, the fuel bowl 5 isprovided withaxially extending arms 7-5 which pass through suitableslots in. -theairscoop 80..and are bolted to the carburetor body.1.Thebottoms of .the fuel bowlS and the'recessin the .throttleibodyfireceiving the fuel bowl define a relief chamber36 -therebetween, and achannel or passage -37.extends:from the chamber 36 through thethrottle-body 3. to theafiow-pas- .sage2 so that the pressure inchamberr36-isaalwaysthe same as that in flow. passagev 2 andself-throttling-of the A.cover 9 is held against the rim of fuel bowl-5by suitable fastenings (not shown). Thearms 75:-may.be integralwithfthecover9 rather .than-with-the..-fuel bowl ..5,.as shown, and in that casethe fuelbowlwill befsecured relative to. the. carburetor. bodylthroughthe cover. 9- ;and 1 .arms Y 75 rather thanthrough the.arms75-.alone. -.The fuel bowlS is formed with a central cylindricalwalLextending-axially therein to form .a nozzle .housing and theinterior .of the fuel bowl '5 .is .divided by suitable .par'titions'into a float chamberat thelowenside whichv.

accommodates a float I7 andcommunicates with a:portion of the interiorabove the'axial cylindrical walLhaving the fuel valve .18 therein.The'float17 is tiltableuand .acts to control. the valve 18 so thatthe'fuel inthe'fioat chamber. is normally maintained at a desired level.The a .remainder of the interior of the bowl'Sjforms .achamber .lHlfromwhich fuel is excluded. The throttle.body 3fis ;formed with .an axialextension which. is. slidable. in the -.axial..cylindrical wall atthecenter of .-the:.bowl..5,.as.-in t the previouslydescribed embodiments.Inrorderttoetfect 276 fuekmetering vneedle, extends axially from.thethrottle -axial movement of the :throt'tle?body-=3 relative'tm'thebowl:.5: and the :carburetorbody :1,:-a-'shaft'f70"is-mounted :in' thechamber H andhas two'- levers r rockably mounted thereon. :One of thelevers rextends at its vouter end through an axialislot" inthe radiallyinward wall 'of .the

chamber.H and into a recess 72 inthe axial extension of .thethrottle'body "3so that rocking -'of that lever r produces axialmovement of the throttlebody. A Bowden cable 121 enters the. cover 9radially. and connects to" the otherlever r which-is. also:rockable ontheshaft 70 and is secured to the first mentioned leverr'by a crosspiece and bolts 71. A spring (not-shown) acts on theassembled zlevers -rto causerocking in' the direction moving the body :3'toward theintakepipe 1and:the:Bowden cable 2liacts to vcause opening movement of :thethrottle .body.

The fuel is supplied through a-pipe 29 connecting radially to thecover'9 and'enters the heat chamber through the valve 18. A fuel passage35 is.formed :in

the cover 9 for conveying the fuel from the floatchamber to'thestructure effecting preliminary mixing of theair and fuel. Thisstructure is of the kind described in detail inzconnection With Figs.4zand 5 and includes 'an;air

intakenozzle and needle valve moving with thethrottle body 3 and a fuelnozzle fixed relative to the cover-9 and cooperating with: the airintake nozzle and the needle .valve to control theadmission of air. andfuel, respectively, for ,the :preliminary mixture. .is dischargedat'theivertex of throttle body 3 from a .nozzle =30 having a dispersingmember P, and is led to .the. nozzle 30 through an axial bore 32 inthe=throttle 'body. The fuelfed into the space between the fuel nozzleThis preliminary mixture and the needle valve enters from a space 49 intheremovable portionu48of the .cover 9, and the air for the preliminarymixture is .supplied .througha passage .13

in the cover 9. Theair. for the-preliminary mixturemay :be-furthercontrolled by avalve 76 in the .passage13 which is controlled by aseparate Bowden cable (not -shown) and acts asa choke to permit the useof an en- '"riched mixture for starting and in cold Weather. Thecarburetor of Fig. 11- is provided with grooves 11 in the surface ofthrottle'body 3 rhaving passages'L extending therefrom to thepreliminary mixing structure and with .passages 0 extending'from thechamber-H to .the preliminary mixing structure for supplyingsupplementary air for atomization and for discharging the'idling .mix

ture in the same manner as thezcorrespondingly numberedparts onv Figs.-4and-5. A screw 23 extends through thebody 1 to form an adjustable idlingstop which: limits the movement of the throttle body 3 toward the. body1, and another screw 78 extends throughthe. cover-9 for engagement withthe throttlebody 3 to provide an ad- ;justable stop for limiting themaximumsize of .theflow passagel2. .The cover. 9 also carriesanadjustment screw v 79.for,controlling the admission of air for idling.The removable portion48.of.the. cover9 which has. the fuel regulatingnozzle secured thereto ispreferably held in .place. by a leaf spring 77,and the cover portion .48. and the fuel nozzle may be .easily removedfor cleaning or .replacement by.'removal..of the spring '77.

The carburetor illustrated in. Fig. 12 is also primarily intended.for..use on. motorcycles and includes -a bodyd forming .a flaringintakepipe anda throttle body'3 which is.movable axially toward. andawayfrom the internal .surfaceofthe bodyl. .As inthe previouslydescribed embodiments, the.confrontingsurfacesof the bodies land:

are similar inshapetothe surfacesd .and e of Figs. .2.and

3. -A.supporting.body.54. is. secured to 'thebody 1. and includes van.axially extending cylindrical member .66 which is slidable .in acylindrical recess of the throttle body 3 so that the. axial movement ofthe. latter is guided by-:.the member 66. Aspring .22.is. interposedbetween \the. supporting body.54. and thethrottle body 3 andcon-.tinuouslyurgesthe latter inthe direction towardtheflaringjntakebodyl.A-.spindlel.8, which. in part formsa body 3 and is formed with anannular recess receiving a forked end of a lever 55 rockably mounted onthe supporting body 54. A Bowden cable 21 is secured to the lever 55 andacts to rock the latter in the direction eifecting axial displacement ofthe spindle 8 and body 3 toward the flaring intake body 1. A ring orstop 64 is mounted on the needle spindle 8 and is engageable against aportion of the support body 54 to limit the movement of the throttlebody 3 under the action of the spring 22.

In order to adapt the carburetor of Fig. 12 for mounting at variousangles to the horizontal, it includes a fuel bowl 5 which is pivoted onthe support body 54 for swinging about the axis of a hollow shaft 60through which the fuel is fed to the preliminary mixing arrangement. Thepivotal mounting of the fuel bowl 5 permits the fuel therein to bemaintained at the correct level with respect to the fuel meteringstructure for the various angles of mounting.

The carburetor of Fig. 12 includes controllable valve means forregulating the admission of air for preliminary mixing. Such air isadmitted radially into a passage system 58 extending through the body 1and support body 54, and a valve 57 is movable axially in the passage tovary the area of the air admitting opening. A spring acts on the valve57 to yieldably urge the latter in the direction restricting theadmission of air for preliminary mixing, and a Bowden cable 56 is alsoattached to the valve 57 for displacing the latter in the directionwhich increases the area of the air admitting opening. The passagesystem 58 connects to an opening 59 extending radially through thecylindrical member 66 of the support body 54.

The arrangement for preliminary mixing is similar to that described inconnection with the embodiments of Figs. 4 and 5, 6 to 10, and 11, andthe needle valve 8 is further provided with a vent 61 through whichadditional air for preliminary mixing is admitted when the throttle body3 has shifted to its idling position so that the vent 61 has moved to alocation outside of a guide bushing 62 which otherwise closes theopening 61. Thus, during idling additional air is provided to reduce theconsumption of fuel during that operating condition.

While various embodiments of the present invention have been describedand illustrated in detail, it is to be understood that the invention isnot limited to these precise embodiments which are merely illustrative,and that various changes and modifications may be effected thereinwithout departing from the spirit or scope of the invention as definedin the appended claims.

What is claimed is:

1. A carburetor for feeding an air-fuel mixture to the intake manifoldof an internal combustion engine; said carburetor comprising a flaringintake pipe body for conducting the air-fuel mixture to the intakemanifold of an associated engine, an onion shaped throttle body, meansmounting said throttle body for axial movement relative to said flaringintake pipe, the confronting surfaces of said flaring intake pipe andsaid throttle body defining a flow passage therebetween which isadjustable in its minimum cross-sectional area by relative axialmovement of said intake pipe and throttle body between a fully closedposition in which said area is substantially zero and a wide openposition in which said area is substantially equal to that of theassociated intake manifold and is located at the tip of said onionshaped throttle body, said confronting surfaces of the flaring intakepipe and the throttle body being shaped so that, in said wide openposition, said flow passage is bounded by hyperbolas corresponding tothe curves of theoretical air flow acceleration whereas, in otherpositions between said wide open and fully closed positions, said flowpassage is bounded by ideal flow curves which include hyperbolas ofreduced dimensions followed by approximately ideal Venturi tube sectionsand then by approximately ideal Laval valve sections which widen to thearea of the intake manifold, and

112 means at said tip of the throttle body for there discharging afuel-air mixture into said flow passage.

2. A carburetor for feeding an air-fuel mixture to the intake manifoldof an internal combustion engine; said carburetor comprising a flaringintake pipe member for conducting the air-fuel mixture to an intakemanifold, 21 throttle body having a generally onion-like outer surfaceand aligned axially with said flaring intake pipe to define a flowpassage between said outer surface of the throttle body and the innersurface of the flaring intake pipe for receiving air radially and fordischarging an air-fuel mixture axially through said intake pipe, meanssupporting said throttle body and intake pipe for relative axialmovement between fully opened and fully closed positions to vary thesectional area of said flow passage, the surfaces of said throttle bodyand intake pipe being formed so that the minimum cross-sectional area ofsaid flow passage therebetween in said fully opened position is equal tothat of the associated intake manifold and is located at the tip of saidthrottle body, said throttle body having means at the tip thereof fordischarging a preliminary air-fuel mixture into said flow passage, andmeans regulated by movement of said throttle body for supplying apreliminary air-fuel mixture to said discharge means and for meteringthe air and fuel components of the preliminary mixture.

3. A carburetor according to claim 2; wherein said throttle body andflaring intake pipe are symmetrical about the aligned axes thereof.

4. A carburetor according to claim 2; further comprising manuallyactuatable means for effecting axial movement of said throttle bodytoward and away from said flaring intake pipe.

5. A carburetor according to claim 4', further comprising meanssupporting said flaring intake pipe for axial movement toward and awayfrom said throttle body, and automatic means acting in response to thepressure at the outlet end of said flaring intake pipe for effectingaxial movement of said flaring intake pipe.

6. A carburetor according to claim 5; wherein said means supporting theintake pipe includes a carburetor housing surrounding said intake pipeand defining a vacuum chamber opening axially against the peripheralportion of said flaring intake pipe in the direction facing toward saidthrottle body, said housing having a passage therein opening at itsopposite ends into said vacuum chamber and adjacent the discharge end ofsaid intake pipe so that the pressure in said vacuum chamber issubstantially the same as that in the intake manifold of an associatedengine, and spring means acting on said flaring intake pipe to yieldablyurge the latter in the axial direction toward said throttle body forreducing the sectional area of said flow passage, whereby a relativelylow pressure in the intake manifold of an associated engine causes saidintake pipe to move axially away from said throttle body in oppositionto said spring means for increasing the sectional area of said flowpassage.

7. A carburetor according to claim 6; including a sealing membraneextending between the periphery of said flaring intake pipe and saidcarburetor housing for closing said vacuum chamber with respect to saidflow passage.

8. A carburetor according to claim 7; including valve means in saidhousing passage operative to throttle flow of air in the direction fromsaid vacuum chamber and to permit free flow of air through said housingpassage in the direction toward said vacuum chamber.

9. A carburetor according to claim 2; further comprising meanssupporting said flaring intake pipe for axial movement toward and awayfrom said throttle body, automatic means acting in response to thepressure at the outlet end of said flaring intake pipe for effectingaxial movement of the latter, means for limiting the axial movement ofsaid flaring intake pipe, and manually actuatable means for effectingaxial movement of said r by saidistationaryssupport and'extendingaxially into said :counterebore .between..-said' outenmetering mer'nberand ingat the tip-of sa'id' throttle body andsaid. body further has:auxiliary atomizer openings in the-outer: surface of said throttle bodyat the zone of said-flow passage Where the pressure changes :from valuesin excess "of atmospheric pressureto a vacuum.

said I needle valve, said outer metering member having an inwardlydirected lipratlthe. edgeithereof remote from-s'a id maindischarge-nozzle opening andthe outer surface'ofsaid.innersmeteringmember varying radially so that an annularairmetering .slot isidefined'between said'lip and outer surface with thearea ofsa'idslot varying in response to axial displacement ofssaid'throttle body, means for sup- 11.'A' carburetor according to iclaim"2;wherein said flaring intake-pipeincludes a-tubularoutlet end portionanda convexly: curvedzrfunnel'portion which is dishshaped at itsperipherysand'connectsrsmoothly to vsaid tubular outlet end portion,a-nd whereinsaid throttle body protrusion into has a concave-conicalvertexiportion :for said funnel portion of the intakepipe.

12. -A carburetor according to claim 10;.wherein said means for.supplying and smeteringzs'the preliminary airfuel mixture includes a:stationarytsupport, co-axial telesaid throttle body, respectively, anddefining an annular air metering slot therebetween, :thesinnerione of.said metering'cylinders being'shaped so that'the' area of said meteringslot varies as said throttle bodyis: moved axially scoping meteringcylinders fixedtosaid supportand to;\

relative to said stationary support, =rneans for :supplyingi air to saidannular-metering slot,:.fuel :metering means for supplying regulatedquantitieslof fuel forxmixing with the air passing through. saidannularmetering .slot, and an axial bore in saidthrottle body extendingito saidmain tdischarge, nozzle for .conveying the preliminary air-fuel .mixture.to..said .main 2 discharge nozzle;

13. A carburetor according to claim 212;:wherein said fuel meteringmeans-includesa fuel meteringneedle valve extending :ax-ially'*inusaid'inner'metering cylinder and movablerelative to the latteriinresponse.toaxial move-:

ment of' said throttle body, 1.-said needle valve. having differentdiameters along'thelength thereof'and said inner metering cylinderandt-needle valve defining an annular fuel metering slot therebetweenwhich variesin 'arearin responsetothe axial movement=of saidfthrottlebody, said. .-:40" needle valvetbeing .fullyzwithdrawn' from said innermetering cylinder when said.throttle:body' is insaid fully opened.position, and: :meansrzfor: supplying :fuel vto the space" between .saidinner. metering: cylinder and said needlev valve.

14."A.:carburetor according to..lclaim 13;. wherein said annular 'fuel:metering :slotais formed Y betweenz'the lower edge of said innermetering cylinder and :said needle valve and said annularair:metering:.-slot lSrfOIH'lCdrbEtWfiCIl'thC upper edge ofthe outermetering cylinder and said inner metering cylinder; and -"wh"ereinsa'idneedle valve is formed with a-conical portion below: said lower edge ofthe inner metering cylinder, saidconical portion having a sharp edge atthe basethereof and.a throttling ring eating with said axial bore'ofsaidthrottle body sothat the metered air is directed against said sharpedge of the conical portion to pick up the metered fuel flowing over 6plying air to said annular air metering slot, the edge of said innermetering member closestto said discharge nozzle openingbeing'inturned-so that an annular fuelmetering slot'is definedbetweensaidinturned'edge and said needle valve, said needle-valve varying indiameter along a portion ofthe length thereof so that the area of saidfuel metering slot varies in responseto ax-ial displacement 'of saidthrottle body, and means for supplying fuel to the space between saidinner metering member and said needle valve.

' 16. A carburetoraccording to claim 15; wherein said means forsupplying fuel-to'the space between 'saidinner metering-member andneedle valve includes a fuel-bowl around said cylindrical stationarysupport, means for maintaining a predetermined level of fuel in saidbowl,

and passage means extending from said bowl to saidspace betweenthe=inner metering member and the needle valve.

17. A carburetor according to claiml6;-wherein said needle valveincludesaconical portion below said inturned edgeof-the innerrneteringmember and having a sharp-edged base, and a throttle ringdisposed-in said counter-bore around sa id'fsharp-edged base sotthat themetered air impinges.- against said sharp-edged base toatomizethe-m'etered fuel flowing over said conical portion-and providea-prjeliminary air-fuel mixture said needle'valve having an axial boreopening into said bore 'leading-to'the'main' discharge nozzle openingand radial passages extending from said axial bore of the needle valveand ppeni-ng'into theannular space between said throttling ring and saidsharp-edgedbase-for carrying the preliminarymixture to said maindischarge nozzle opening.

18. A carburetor according to claim 17; wherein said axialprojection ofthe'throttle body has an annular'cavity adjacent the end=portionfof saidneedle valve closestrto said m'ainfldischarge =nozzle opening, anannular=space aroundsaid-'end portion of theneedle .valve communicatingsaid cavity with theaxial bore leading to said 'main discharge nozzleopening, passage means in said'throttle "bodyextending-fromsaid cavityand opening at arlocaextending around saidbase' of the conical, portionvto define an annulanthrottling slotitherebetween,.comrnuniportion of theneedle valve.

tion of relatively highrpressurevso that: secondary air for atomizationis -normally supplied to said cavity for;mix-

ture with the preliminaryait-fuel mixture atv saidend 19.A':carburetoriaccording to claim 18; whereinsaid throttle bodyhasauxiliary discharge nozzle openings in the outer surfacei'there'of atlocationswhichrarersubject "to r elatively low-pressure: when :saidthrottle body. .iswdisplaced toward said flaring intake pipe to theidling position, and passages in said throttle body extending between 0said cavity and said auxiliary openings so that the prefuel mixtureincludes a central axial projection on said throttle body extending inthe direction away from said flaring intake pipe, a stationarycylindrical support around said central projection, said throttle bodyand projection having an axial bore extending therethrough to said maindischarge nozzle opening and terminating in an enlarged lirninarymixture is drawn from said needle valve bore into said cavity anddischarged at said auxiliary openings when said throttle body is in itsidling position.

20.'A carburetor according to claim 19; wherein said auxiliary openingsare located at different levels on said throttle body so that air entersthe auxiliary openings subjected to relatively high pressure and thefuel-air mixture is discharged through the auxiliary openings subjectedto relatively low pressure.

21. A carburetor according to claim 19; wherein said inner and outercylindrical metering members are axially adjustable relative to saidstationary support and said projection, respectively, for varying therelationship between the metering of the fuel and air and the positionof 5 said throttle body.

22. A carburetor according to claim 15; including an atomizer plateextending across said main discharge nozzle opening at the vertex ofsaid throttle body and spaced axially from said vertex to effectdispersion of the fuelair mixture issuing from said main nozzle opening.

23. A carburetor according to claim 15; wherein said means for supplyingfuel to the space between the inner metering member and the needle valveincludes a fuel bowl around said cylindrical support and having acylindrical outer wall, said throttle body having a cylindrical recessopening in the direction away from said flaring intake pipe andreceiving said fuel bowl, said throttle body having vent means extendingbetween said flow passage and the space between the bottoms of said fuelbowland said recess receiving the fuel bowl to prevent self-throttlingof the carburetor.

24. A carburetor according to claim 2; further comprising air filteringmeans extending across the radially outward inlet end of said flowpassage.

25. A carburetor according to claim 24; wherein said means for supplyinga preliminary air-fuel mixture to said discharge means includes a fuelbowl, means operative to normally maintain fuel up to a predeterminedlevel in said bowl, means for rendering the last mentioned meansinoperative to cause over-flowing of fuel from said bowl, and passagemeans extending from said bowl above said predetermined level andopening adjacent said filter so that overflowing fuel is directedagainst said filter to wet the surface of the latter for additionalatomization for starting.

26. A carburetor according to claim 15; wherein said means for supplyingfuel to the space between said inner metering member and said needlevalve includes a fuel bowl around said stationary cylindrical supportand at an axial location between inner metering member and the vertex ofsaid throttle body so that, when the carburetor is mounted on a vehiclewith its axis horizontal and the throttle body having its'vertexpointing in the direction of movement of the vehicle, the fuel will flowdownwardly from said bowl to said space between the inner meteringmember and the needle valve during uphill driving of the vehicle.

27. A carburetor according to claim 26; including hollow shaft meanspivotally mounting said fuel bowl on the stationary support, meansconducting fuel from said pivoted bowl through said hollow shaft meansto said space between the inner metering member and the needle valve,and means for maintaining fuel at a predetermined level within saidpivoted bowl so that the level of fuel in said bowl always is the samein relation to said inner metering member and needle valve withoutregard to the angle at which the carburetor is mounted on a vehicle.

28. A carburetor according to claim 2; wherein said means supporting thethrottle body includes a fixed housing having a cylindrical wall andenclosing a fuel bowl, said throttle body having a cylindrical recessreceiving said cylindrical fixed housing and movable rotationally andaxially on the latter, mating threads of steep pitch on the adjacentcylindrical walls of said recess and fixed housing, and manuallyactuatable means for effecting rotation of said throttle body relativeto said fixed housing to thereby cause axial movement of said throttlebody.

29. A carburetor according to claim 15; wherein said means for supplyingfuel to the space between the inner metering member and the needle valveincludes a fuel bowl around said stationary support, means for supplyingfuel to said bowl, valve means for regulating the supply of fuel to saidbowl, and a float member posi tioned in said bowl to actuate said valvemeans and free to tilt and to rise and fall within said bowl.

30. A carburetor according to claim 29; wherein said throttle body has arecess therein to accommodate said fuel bowl, and further including fuelfilter means and a dirt trap chamber interposed in said means supplyingfuel to the bowl and positioned in said recess of the throttle body.

31. A carburetor according to claim 30; wherein said fuel filter meansand dirt trap chamber are included in a cover for said fuel bowl, andaxially extending securing elements holding together said cover, saidsupport member and the fuel bowl, and said support means for the flaringintake pipe.

32. A carburetor according to claim 31; wherein said securing elementsconsist of axial arms of elongated cross-section having the major axisof the cross-section extending radially to facilitate radial flow of airinto said flow passage.

33. A carburetor according to claim 32; wherein said throttle body issubstantially concave at the vertex portion thereof and includes acurved air scoop extending from the periphery thereof and facing in thedirection toward said flaring intake pipe to direct air moving past thecarburetor radially inward toward said vertex of the throttle body.

34. A carburetor according to claim 33; wherein said air scoop is formedwith radial slots through which said axial securing arms extend.

35. A carburetor according to claim 2; wherein said throttle body has avertex portion in the form of a chisellike blade with said dischargingmeans including discharge orifices opening along the edge of saidbladelike vertex portion; and wherein said flaring intake pipe has anoval outlet portion with its major axis parallel to said edge of thevertex portion.

References Cited in the file of this patent UNITED STATES PATENTS1,973,362 Weiertz et al. Sept. 11, 1934 1,990,702 Leibing Feb. 12, 19352,034,048 Leibing et al. Mar. 17, 1936 2,167,892 Kent et a1 Aug. 1, 1939

